// Copyright (c) 2012 The Chromium Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

#ifndef MEDIA_AUDIO_SCOPED_TASK_RUNNER_OBSERVER_H_
#define MEDIA_AUDIO_SCOPED_TASK_RUNNER_OBSERVER_H_

#include "base/macros.h"
#include "base/memory/ref_counted.h"
#include "base/message_loop/message_loop.h"

namespace base {
class SingleThreadTaskRunner;
class WaitableEvent;
}

namespace media {

// A common base class for AudioOutputDevice and AudioInputDevice that manages
// a task runner and monitors it for destruction. If the object goes out of
// scope before the task runner, the object will automatically remove itself
// from the task runner's list of destruction observers.
// NOTE: The class that inherits from this class must implement the
// WillDestroyCurrentMessageLoop virtual method from DestructionObserver.
class ScopedTaskRunnerObserver
    : public base::MessageLoop::DestructionObserver {
public:
    explicit ScopedTaskRunnerObserver(
        const scoped_refptr<base::SingleThreadTaskRunner>& task_runner);

protected:
    ~ScopedTaskRunnerObserver() override;

    // Accessor to the loop that's used by the derived class.
    const scoped_refptr<base::SingleThreadTaskRunner>& task_runner()
    {
        return task_runner_;
    }

private:
    // Call to add or remove ourselves from the list of destruction observers for
    // the message loop.
    void ObserveLoopDestruction(bool enable, base::WaitableEvent* done);

    // A pointer to the task runner. In case it gets destroyed before this object
    // goes out of scope, PostTask() etc will fail but not crash.
    scoped_refptr<base::SingleThreadTaskRunner> task_runner_;

    DISALLOW_COPY_AND_ASSIGN(ScopedTaskRunnerObserver);
};

} // namespace media.

#endif // MEDIA_AUDIO_SCOPED_TASK_RUNNER_OBSERVER_H_
